GDF15 and glioma: In order to identify possible connections between GDF15 and RSU-1 with regard to glioma cell invasion, we examined the RSU-1 mRNA expression upon hrGDF-15 treatment and found that in H4 cells, which express low RSU-1 and high GDF-15 levels, RSU-1 was strongly upregulated following hrGDF-15 treatment both at the mRNA (Figure 3A) and protein level (Figure 3B,C).